From: Daniel Vetter <daniel@ffwll.ch>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Leon Romanovsky <leon@kernel.org>,
linux-rdma <linux-rdma@vger.kernel.org>,
John Hubbard <jhubbard@nvidia.com>,
Maling list - DRI developers <dri-devel@lists.freedesktop.org>,
Doug Ledford <dledford@redhat.com>,
Daniel Vetter <daniel.vetter@intel.com>,
Christian Koenig <christian.koenig@amd.com>,
Jianxin Xiong <jianxin.xiong@intel.com>
Subject: Re: [PATCH v16 0/4] RDMA: Add dma-buf support
Date: Fri, 5 Feb 2021 16:53:04 +0100 [thread overview]
Message-ID: <YB1p4Bpmz0yFcbEf@phenom.ffwll.local> (raw)
In-Reply-To: <20210205154319.GT4247@nvidia.com>
On Fri, Feb 05, 2021 at 11:43:19AM -0400, Jason Gunthorpe wrote:
> On Fri, Feb 05, 2021 at 04:39:47PM +0100, Daniel Vetter wrote:
>
> > > And again, for slightly older hardware, without pinning to VRAM there is
> > > no way to use this solution here for peer-to-peer. So I'm glad to see that
> > > so far you're not ruling out the pinning option.
> >
> > Since HMM and ZONE_DEVICE came up, I'm kinda tempted to make ZONE_DEVICE
> > ZONE_MOVEABLE (at least if you don't have a pinned vram contigent in your
> > cgroups) or something like that, so we could benefit from the work to make
> > sure pin_user_pages and all these never end up in there?
>
> ZONE_DEVICE should already not be returned from GUP.
>
> I've understood in the hmm casse the idea was a CPU touch of some
> ZONE_DEVICE pages would trigger a migration to CPU memory, GUP would
> want to follow the same logic, presumably it comes for free with the
> fault handler somehow
Oh I didn't know this, I thought the proposed p2p direct i/o patches would
just use the fact that underneath ZONE_DEVICE there's "normal" struct
pages. And so I got worried that maybe also pin_user_pages can creep in.
But I didn't read the patches in full detail:
https://lore.kernel.org/linux-block/20201106170036.18713-12-logang@deltatee.com/
But if you're saying that this all needs specific code and all the gup/pup
code we have is excluded, I think we can make sure that we're not ever
building features that requiring time-unlimited pinning of ZONE_DEVICE.
Which I think we want.
Cheers, Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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next prev parent reply other threads:[~2021-02-05 15:53 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-15 21:27 [PATCH v16 0/4] RDMA: Add dma-buf support Jianxin Xiong
2020-12-15 21:27 ` [PATCH v16 1/4] RDMA/umem: Support importing dma-buf as user memory region Jianxin Xiong
2020-12-15 21:27 ` [PATCH v16 2/4] RDMA/core: Add device method for registering dma-buf based " Jianxin Xiong
2020-12-15 21:27 ` [PATCH v16 3/4] RDMA/uverbs: Add uverbs command for dma-buf based MR registration Jianxin Xiong
2020-12-15 21:27 ` [PATCH v16 4/4] RDMA/mlx5: Support dma-buf based userspace memory region Jianxin Xiong
2021-01-11 15:24 ` [PATCH v16 0/4] RDMA: Add dma-buf support Xiong, Jianxin
2021-01-11 15:42 ` Jason Gunthorpe
2021-01-11 17:44 ` Xiong, Jianxin
2021-01-11 17:47 ` Alex Deucher
2021-01-11 17:55 ` Xiong, Jianxin
2021-01-12 12:49 ` Yishai Hadas
2021-01-12 18:11 ` Xiong, Jianxin
2021-01-21 16:59 ` Jason Gunthorpe
2021-02-04 7:48 ` John Hubbard
2021-02-04 13:50 ` Alex Deucher
2021-02-04 18:29 ` Jason Gunthorpe
2021-02-04 18:44 ` Alex Deucher
2021-02-04 19:00 ` John Hubbard
2021-02-05 15:39 ` Daniel Vetter
2021-02-05 15:43 ` Jason Gunthorpe
2021-02-05 15:53 ` Daniel Vetter [this message]
2021-02-05 16:00 ` Jason Gunthorpe
2021-02-05 16:06 ` Daniel Vetter
2021-02-05 20:24 ` John Hubbard
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